It is a common problem that land in particular regions, e.g. close to a waterway or beach, can be prone to flooding on a regular, intermittent or unpredictable basis. Furthermore, climate change and extreme weather events potentially increases the probability of flooding in a given area and/or introduces risk to places where there had never previously been a problem. This issue has particular significance in the UK and will be an ever increasing problem as population density increases.
Real estate in flood prone areas is often desirable for aesthetic reasons but can be uninsurable due to the high probability of damage to conventional building structures. Conversely, land in flood prone areas can be obtained at lower cost, such that it is attractive for social housing, but presents a high risk as a building project.
It is clear that the ever increasing likelihood of flood events has created a need for housing which can resist and/or otherwise survive periods of flood.
The most common strategy for reacting to a flood situation is to build barriers, e.g. of sandbags, that deflect water around a home or larger collection of buildings. Such solutions must be deployed rapidly which presents significant challenges and, in any event, the degree of protection is limited by height of such barriers which, in turn, is limited by resources and other practical considerations.
In countries that have large regions under constant threat of inundation, such as The Netherlands, other approaches to the problem of flooding have been explored. A popular approach is to utilise floating structures/foundations upon which to build a house. Indeed, such technology is often used to produce permanently floating houses which can be located on a river or canal, etc.
Known types of floating house system include a hull type and a raft type. The hull type excludes water in the same way a boat does and, at a certain depth of water, becomes buoyant. The raft type incorporates buoyancy into a deep supporting foundation slab. The completed building is typically moored to a post, e.g. by steel arms, and can rise and fall with flood waters or tide. These types of design are appropriate for water fronts or controlled flooding locations; however, they are not suited for situations where there are high flow flood waters and where flood debris is likely. It is also noteworthy that the UK Housing Act gives security of tenure to people living legally on land, but floating dwellings such as house boats do not have the same security of tenure. Furthermore, with regard to hull and raft types of floating house, there is a lack of control when returning the property to ground level after flood waters recede.
Another form of floating home is an amphibious house type which is secured on thick steel posts. Such designs can be more resilient to flood because of the more secure structure. An amphibious house uses a passive lifting system based on buoyancy where it may have a hollow concrete basement and telescopic piles allowing the house to rise with water level. One problem associated with such designs is that there is no way to control the lowering of the house when waters recede which could lead to debris being trapped underneath the base, resulting in an uneven resting position. Similarly, these solutions are not suited to occasionally flooded land because of the high build price (roughly twice a traditional house).
WO98/22663 describes a floatation system for a building that includes a watertight basement that can rise and fall in relation to guideposts located at the corners. The guideposts have a ratchet system to maintain the building at a desired height, by virtue of rising water. The preferred embodiment also envisages the use of pressurised cylinders for lifting the building prior to a surge of flood water. Nevertheless, such an elaborate system is very expensive to build and unsuited for social housing projects intended to be erected on low cost land.
WO2006/100698, DE10234049, WO96/30602 and US2005/092218 describe buildings that are generally retractable into the ground for the purposes of storm, i.e. high wind, damage prevention. These constructions are not suitable for flood risk mitigation and, in fact, increase the likelihood of damage.